We’re all familiar with the classic old “7 Segment” displays. You know, the little red numbers you could get from radio shack. Anyway, I had a few extra parts laying around, and had an idea for what I could use them for, so I made a little display using four of them. For those who just want the pictures, here they are. For those who want the details, read on.
Alright, now for the nitty gritty. In reality though, it’s not really that gritty.
I got some free samples from Maxim-IC a while back, and among them were two MAX6956 I/O Port Expander / LED Driver chips. These two chips can be programmed with a unique address, so that I can use the same two wires from the arduino to control both of them. Via this, I can control 20 pins on each chip. (40 total between the two.)
They also have a built in current limiting mode for driving LEDs so you don’t burn them out. This is set via the external resistor seen in some of the pictures.
I programmed the arduino to keep time, and then turn on and off the appropriate pins to create the numbers on the segments. Pretty simple really. It was actually a lot harder getting all of those little wires through the holes in the back board all at the same time.
The whole assembly is run by four conductor phone line which carries the power lines, and the two data lines.
Really though, the clock function wasn’t my plan for this little project. It was just a test to make sure it worked, and enjoy my handiwork while I finished my other project. The goal is to have it be a voltage display on a power supply I’m building. I won’t spoil the next blog post which should be about that. (Theoretically I’m close to finishing it.) However, it’s safe to talk a little bit about it.
I got most the parts for it from the same free stuff pile that I got these little displays from, and the same one I got the EL Display from. (Yes, he had a lot of stuff)(Also, for credit where credit is due, the girly pointed it out to me on craigslist, and tolerates my massive piles of electronics crap. Thanks hon!)
Anyway, the last I’ll say about it, is that it’s massive, both physically and electrically. So it goes without saying that I’m excited to see the results.